Hindawi Publishing Corporation Journal of Nanomaterials Volume 2013, Article ID 301674, 5 pages http://dx.doi.org/10.1155/2013/301674 Research Article Area-Selective ZnO Thin Film Deposition on Variable Microgap Electrodes and Their Impact on UV Sensing Q. Humayun, M. Kashif, and U. Hashim Nano Biochip Research Group, Institute of Nano Electronic Engineering (INEE), Universiti Malaysia Perlis (UniMAP), 01000 Kangar, Perlis, Malaysia Correspondence should be addressed to Q. Humayun; qhumayun2@gmail.com Received 4 January 2013; Revised 7 April 2013; Accepted 20 May 2013 Academic Editor: Gong Ru Lin Copyright © 2013 Q. Humayun et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ZnO thin flms were deposited on patterned gold electrodes using the sol-gel spin coating technique. Conventional photolithogra- phy process was used to obtain the variable microgaps of 30 and 43 m in butterfy topology by using zero-gap chrome mask. Te structural, morphological, and electrical properties of the deposited thin flms were characterized by X-ray difraction (XRD), scanning electron microscope (SEM), and Keithley SourceMeter, respectively. Te current-voltage (I -V) characterization was performed to investigate the efect of UV light on the fabricated devices. Te ZnO fabricated sensors showed a photo to dark current (I ph /I d ) ratios of 6.26 for 30 m and 5.28 for 43 m gap electrodes spacing, respectively. Dynamic responses of both fabricated sensors were observed till 1V with good reproducibility. At the applied voltage of 1 V, the response time was observed to be 4.817 s and 3.704 s while the recovery time was observed to be 0.3738 s and 0.2891 s for 30 and 43 m gaps, respectively. Te signal detection at low operating voltages suggested that the fabricated sensors could be used for miniaturized devices with low power consumption. 1. Introduction Te emergence of nanomaterial-based devices in the market motivates the researchers to fabricate diferent low-cost high- throughput sensors. Ultraviolet (UV) photodetectors have drawn a great deal of attention in recent years in various commercial and military applications, such as secure space- to-space communications, pollution monitoring, water ster- ilization, fame sensing, and early missile plume detection [1]. Zinc oxide has attracted much research attention because of its unique properties such as high surface-to-volume ratios [2], wide direct band gap (E  = 3.37 eV), and high exciton binding energy (60 meV). In comparison with GaN, ZnO thin flm have maximum electron saturation velocity; therefore, ZnO-based photodetectors can attain the maximum opera- tion speed [3]. ZnO nanostructures can be synthesized via variety of methods including MOCVD [4], thermal evaporation [5], molecular beam epitaxy (MBE) [6], electrochemical depo- sition [7], spray pyrolysis [8], and sol-gel [9]. Among these methods, the sol-gel technique is the simplest and least expensive. One-dimensional ZnO nanostructures are gaining great attention because of their potential applications in nanoscale electronic and optoelectronic devices [10, 11]. Metal-semiconductor-metal (MSM) Schottky barrier diodes are attractive photodetectors because of their low dark current, fast response, superior responsivity, and also direct compatibility with modern high-speed integrated cir- cuitry [12]. To fabricate sensitive and selective metal-semi- conductor-metal (MSM) photosensor, the most signifcant factor is to obtain large Schottky barrier height at interface, because large Schottky barrier height generates small leakage current and maximum breakdown voltage which exaggerate the responsivity and photo-to-dark-current contrast ratio [13]. Terefore, verities of photo-sensors including p-n jun- ction, metal-semiconductor-metal, and Schottky diodes have been fabricated, but due to simple structure and low cost, metal-semiconductor-metal photo sensors are getting the market value [14]. However, the maximum decay time and maximum dark current are the failure of photoconductive kind photo sensors, but still all the reported photoconductive type ultraviolet sensors perform maximum gain [15].